The present invention relates to methods and devices for transporting sheets. A sheet to be transported or conveyed in a sheet processing machine with at least one conveying cylinder is fed to the conveying cylinder in two successive passes.
The document xe2x80x9cSheet Feed Systemxe2x80x9d Research Disclosure, December 1997, XP000735770, page 944, describes a method for conveying sheets in a sheet processing machine having a conveying cylinder and the following steps:
a sheet is fed to the conveying cylinder,
this sheet is removed from the conveying cylinder by the use of a pair of rollers and a belt conveyor system,
a position of this sheet is checked,
the sheet is thereafter conducted to the conveying cylinder a second time for perfecting.
FR-A-2 401 027 describes a device for conveying sheets in a sheet processing machine, having a conveying cylinder, to which a first sheet feeding device and a first sheet removal device, as well as a second sheet feeding device and a second sheet removal device are assigned.
DE 29 55 96 C1 shows two conveying drums assigned to a conveying cylinder, which are used as a sheet feeding and removing device.
The present invention is based on the object of providing a method and devices for transporting sheets.
In accordance with the invention, this object is attained by using a sheet processing machine having at least one conveying cylinder. The sheet to be processed is fed to the conveying cylinder. This sheet is removed from the conveying cylinder and is then fed a second time to the conveying cylinder. The sheet may be conveyed by a chain or by a belt conveying system. The sheet is typically processed on the conveying cylinder.
With the method of the present invention and with the associated device, it is possible, in an advantageous manner, to retrofit existing presses with a device for executing a further processing step, in particular for performing an inspection.
If an inspection is performed prior to further processing steps, for example prior to numbering or printing, further processing can be controlled as a function of the inspection result, i.e. numbering can be omitted, for example.
In the present preferred embodiment, a first side of a sheet is checked and its second side numbered. In contrast to an inspection later, damage to the numbered side is avoided because of the inspection being performed prior to numbering.